You will need a timer for this one!
Time the first exercise in your Combo (ie, 50 x Mountain Climbers). You will then drop to a plank for the equivalent amount of time.
Repeat the Mountain Climbers for 100 reps, then drop to a plank for the same amount of time. Repeat for all reps in all combos!
Combo #1 : Mountain Climber VS Plank : Round 1 x 50 Round 2 x 100 Round 3 x 150
Combo #2: Chest to Floor Burpee VS Wall Sit: Round 1 x 10 Round 2 x 20 Round 3 x 30
Combo #3: Push up VS Pulsing Pushup: Round 1 x 10 Round 2 x 20 Round 3 x 30